Price tag for 700 miles of border fencing: high and hard to pin down

The feds have already build 670 miles of fence on the border, like this one near Naco, Ariz. A deal in the Senate calls for the completion of 700 more miles.

A plan for 700 more miles of fencing along the southwest U.S. border — part of a immigration-bill deal forged in the Senate this week — would come with a mammoth and unpredictable price tag, judging by past efforts.

The original legislation crafted by the bipartisan Gang of Eight set aside $1.5 billion for fencing — and that was before a deal was struck with Republican senators to add more to the massive border security and fencing proposal. So how much would a new bigger border fence cost?

Customs and Border Protection spent $2.4 billion between 2006 and 2009 to complete 670 miles of border fence, and the vast majority of that was single-layer — one line of fencing designed to keep either pedestrians or vehicles from crossing into the United States, according to a Government Accountability Office report.

The new plan calls for a double-layer fence — two parallel barriers on either side of a corridor manned by Border Patrol — that would require more land acquisition, more supplies and more labor to build.

There is no firm cost for the fence outlined in the "border surge" agreement announced Thursday, and the price of previous fence construction has varied wildly.

A 2009 analysis by the GAO found that the cost of pedestrian fencing ranged between $400,000 and $15 million per mile with an average of $3.9 million a mile. The price of less expensive vehicle fencing ran anywhere from $200,000 to $1.8 million a mile, for an average of $1 million a mile.

That same year, Customs and Border Protection set aside $58 million to build a 3.5 mile stretch of fence along "difficult terrain" in San Diego, according to the GAO, an investigative arm of Congress.

"The per mile costs to build the fencing varied considerably because of the type of fencing, topography, materials used, land acquisition costs, and labor costs, among other things," the office's report said.

For example, while some 2008 contracts were being finalized, estimates began to balloon because the construction boom in Texas led to labor shortages and rising steel and cement prices, budget watchdogs noted.

And then there's the need to commandeer private land. The government can seize private property under eminent domain, but the costs of that action may not manifest themselves until legal battles are resolved.

Frederic J. Brown / AFP - Getty Images file

This US-Mexico 'border-fence' runs right into the Pacific Ocean near San Diego. The cost of building such fences has ranged wildly making it difficult to pinpoint the price tag of expansion.

Scott Nicol, chair of the Sierra Club Borderlands Team, which opposes fence expansion because of the threat to wildlife, expects much of the new double-layer fence would run through south Texas, where "you do have a lot of people who are just like, 'I'm not going to sell my land.'"

An Associated Press analysis of court documents last year found that when homeowners reject the feds' initial offers to buy their borderlands, the cost skyrockets.

The Nature Conservancy balked at an offer of $114,000 for a fence on its land in the Rio Grande Valley in south Texas, and ultimately settled for $1 million. A developer in Brownsville, Texas, was offered $233,000 but ended up with $4.7 million three years later.

Building border fortifications didn't always cost so much. Earlier fence projects were carried out using scrap metal and Border Patrol or National Guard laborers, but as more and more barriers were approved and deadlines imposed, private contractors overseen by the Army Corps of Engineers took over the work.

For a sense of the scope of the contracts, consider a 2009 push to erect 38 miles of 19-foot fence near El Paso, Texas. The contractor, New Mexico-based Kiewit, said in a summary that more than 1,100 people and 600 pieces of equipment were mobilized to complete it in four months. The total cost of that segment: $170 million.

Like any large government initiative, border security is not immune from waste. A 2011 report by the Inspector General for the Department of Homeland Security found that Customs and Border Protection needlessly spent about $69 million by botching the order of steel and approving a high-priced subcontractor.

The payoff of all this infrastructure is unclear. Illegal entries to the United States fell 69 percent between 2006 and 2011, while drug and contraband seizures nearly doubled, the GAO said in a March report. At the same time, the report said, Customs could not account for the impact of the fence.

In response to a 2009 recommendation, the agency undertook an outside analysis to measure the effect of border fencing. Last year, officials said that based on preliminary results it will take another three to five years to come up with a "credible assessment" of how well the first 670 miles of fence is working.

If the full Congress eventually approves another 700 miles of double-layer barrier as part of an overall immigration bill, the cost-effectiveness may not be clear until after the last fence post is driven into the ground.